Aspidoras maculosus Nijssen & Isbrücker, 1976

Tencatt, Luiz Fernando Caserta, Britto, Marcelo R., Isbrücker, Isaäc Jan Hendrik & Pavanelli, Carla Simone, 2022, Taxonomy of the armored catfish genus Aspidoras (Siluriformes: Callichthyidae) revisited, with the description of a new species, Neotropical Ichthyology (e 220040) 20 (3), pp. 1-159 : 85-95

Aspidoras maculosus Nijssen & Isbrücker, 1976

( Figs. 44–45 )

Aspidoras maculosus Nijssen & Isbrücker, 1976:119 (original description; type locality: rio Paiaiá , Bahia State, Brazil). — Reis , 2003:292 (listed). — Britto et al., 2005:478 (morphological comparison). — Ferraris , 2007:109 (listed). — Tencatt, Bichuette, 2017:8 (morphological comparison).

Aspidoras rochai (non Ihering, 1907) Ellis, 1913:394 (listed; pl. XXVI, fig. 3; partim).

Diagnosis. Aspidoras maculosus can be distinguished from its congeners, with exception of A. depinnai , A. fuscoguttatus , A. poecilus , A. raimundi , and A. rochai , by having anterior portion of infraorbital 1 with well-developed laminar expansion, surpassing middle of nasal capsule (vs. ranging from strongly reduced, at same level as posterior margin of nasal capsule, to moderately developed, reaching middle of nasal capsule in A. albater ; ranging from strongly reduced, not reaching or at same level as posterior margin of nasal capsule, to moderately developed, reaching middle of nasal capsule in A. mephisto ; extremely well developed, reaching or surpassing anterior margin of nasal capsule in A. belenos ; moderately developed, reaching middle of nasal capsule in A. azaghal ; ranging from poorly developed, slightly surpassing posterior margin of nasal capsule, to moderately developed, reaching middle of nasal capsule in A. aldebaran and A. lakoi ; strongly reduced expansion, not reaching or at same level as posterior margin of nasal capsule in A. psammatides and A. velites ); it differs from A. depinnai by having small dark brown or black spots on dorsal fin (vs. spots absent); from A. fuscoguttatus by the following combination of features: presence of relatively large, well-defined dark brown or black blotches on top of the head (vs. absence), inner laminar expansion of infraorbital 1 moderately developed (vs. generally well developed), and a narrow frontal bone, with width slightly smaller than half of entire length (vs. generally relatively wide, with width equal to or slightly larger than half of entire length); from A. poecilus by the following combination of features: dark brown or black stripe from anteroventral portion of orbit to upper lip lateral area, when present, less evident (vs. generally present and more evident), and by dark brown or black large patches on dorsal fin generally absent (vs. generally present); from A. raimundi by having the following combination of features: absence of large and intensely pigmented dark brown or black blotch on dorsal fin (vs. generally present), and markings on ventrolateral body plates generally present and clearly more numerous, not considering the number of blotches in the series along flank midline (vs. markings, when present, clearly scarcer); from A. rochai by the presence of a narrow frontal bone, with width slightly smaller than half of entire length (vs. relatively wide, with width equal to or slightly larger than half of entire length).

Description. Morphometric data presented in Tab. 7; morphometric data of the holotype available in Nijssen, Isbrücker (1976:110, tab. 1). Head compressed with convex dorsal profile; somewhat triangular or trapezoid in dorsal view. Snout moderately developed and rounded. Head profile convex from tip of snout to anterior nares; ascending slightly convex to nearly straight from this point to dorsal-fin origin; region of orbit and/or parieto-supraoccipital slightly concave in some specimens. Profile slightly convex along dorsal-fin base. Postdorsal-fin body profile slightly concave to adipose-fin spine; slightly concave from this point to caudal-fin base. Ventral profile of body slightly convex from isthmus to pelvic-fin origin; region of gill opening slightly concave in some specimens; nearly straight from this point to anal-fin origin; slightly concave until caudal-fin base. Body roughly elliptical in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin.

Eye rounded, located dorso-laterally on head; orbit delimited dorsally by lateral ethmoid, frontal and sphenotic, ventrally by infraorbitals. Anterior and posterior nares close to each other, only separated by flap of skin. Anterior naris tubular. Posterior naris close to anterodorsal margin of orbit, separated from it by distance equal to or slightly smaller than naris diameter. Mouth small, subterminal, width larger than bony orbit diameter. Maxillary barbel moderate to large in size, ranging from not reaching to surpassing anteroventral limit of gill opening. Outer mental barbel slightly larger than maxillary barbel. Inner mental barbel fleshy, with base close to its counterpart. Lower lip moderately developed, forming small semicircular or triangular fleshy flap; with two triangular fleshy flaps in some specimens. Small rounded papillae covering entire surface of all barbels, upper and lower lips, snout and isthmus.

Mesethmoid short; anterior tip long, slightly larger than 50% of entire bone length (see Britto, 2003:123, ch. 1, state 0; fig. 1A); posterior portion wide, entirely covered by thick layer of skin. Nasal slender, curved laterally, inner margin with moderately-developed laminar expansion; outer margin with reduced laminar expansion; mesial border generally contacting only frontal.

Frontal elongated, narrow, with width slightly smaller than half of entire length ( Fig. 3A ); anterior projection short, with size smaller than nasal length; some areas of anterior margin covered by thick layer of skin. Frontal fontanel relatively small, ellipsoid or somewhat rhomboid; posterior tip extension not entering anterior margin of parieto-supraoccipital. Sphenotic somewhat trapezoid, contacting parieto-supraoccipital dorsally, pterotic-extrascapular posteriorly, second infraorbital ventrally and frontal anteriorly. Pterotic-extrascapular roughly pipe-shaped, with posteriormost portion contacting first lateral-line ossicle, and ventral margin contacting opercle and cleithrum; posterior expansion almost entirely covering lateral opening of swimbladder capsule, leaving slender pseudotympanic area on its dorsal margin covered only by thick layer of skin. Parieto-supraoccipital wide, posterior process strongly reduced to poorly developed; not contacting nuchal plate. Parieto-supraoccipital medial keel expanded ventrally; laminar, with posterior portion not reaching tip of posterior process. Parieto-supraoccipital fontanel small, roundish; located medially on parieto-supraoccipital; fontanel occluded, reduced to a small fossa, in some specimens.

Two laminar infraorbitals with minute odontodes; infraorbital 1 large, ventral laminar expansion generally extremely well developed; well developed in some specimens; anterior portion with well-developed laminar expansion, surpassing middle of nasal capsule ( Fig. 46 ); inner laminar expansion moderately developed ( Fig. 5C ); small portions of external surface covered by thick layer of skin; infraorbital 2 small, generally slender; slightly more compact in some specimens; generally with posterior laminar expansion moderately developed; or poorly developed; inner laminar expansion moderately developed; posteroventral margin contacting posterodorsal ridge of hyomandibula; dorsal tip contacting only sphenotic; small portions of external surface covered by thick layer of skin ( Fig. 46 ). Posterodorsal ridge of hyomandibula, close to its articulation with opercle, oblong, relatively slender; exposed; dorsal ridge of hyomandibula, between pterotic-extrascapular and opercle, covered by thick layer of skin; variably covered by thin layer of skin, exposed; exposed areas generally bearing small odontodes. Interopercle with posterior portion generally exposed; somewhat triangular, anterior projection moderately developed. Preopercle relatively slender, elongated, minute odontodes sparse on external surface. Opercle compact in shape, width larger than half of its length; free margin convex; posterodorsal region variably with smoothly concave area; without serrations and covered by small odontodes; some portions of bony distal margin smoothly irregular in some specimens.

Four branchiostegal rays decreasing in size posteriorly. Hypobranchial 2 somewhat triangular, tip ossified and directed towards anterior portion, posterior margin cartilaginous; ossified portion well developed, about twice size of cartilaginous portion. Five ceratobranchials with expansions increasing posteriorly; ceratobranchial 1 with small process on anterior margin of mesial portion; ceratobranchial 3 with continuous postero-lateral margin; ceratobranchial 5 toothed on postero-dorsal surface, 26 to 29(1) teeth aligned in one row. Four epibranchials with similar size; epibranchial 2 slightly larger than others, with small pointed process on laminar expansion of posterior margin; epibranchial 3 with triangular uncinate process on laminar expansion of posterior margin. Two wide pharyngobranchials (3 and 4), pharyngobranchial 3 with triangular laminar expansion on posterior margin; triangular laminar expansion with rounded notch. Upper tooth plate oval, with 32 to 36(1) teeth aligned in two rows on posteroventral surface.

Lateral-line canal entering neurocranium through pterotic-extrascapular, branching twice before entering sphenotic: pterotic branch with single pore; preoperculomandibular branch conspicuously reduced, with single pore opening close to postotic main canal; postotic main canal widens just posterior to pterotic branch. Sensory canal continuing through pterotic-extrascapular, entering sphenotic as temporal canal, which splits into two branches: one branch giving rise to infraorbital canal, other branch entering frontal through supraorbital canal, both with single pore. Supraorbital canal branched, running through nasal bone. Epiphyseal branch of supraorbital canal relatively long, with pore opening close to frontal fontanel; or slightly shorter, with pore opening closer to supraorbital main canal. Nasal canal with three openings, first on posterior edge, second on posterolateral portion and third on anterior edge; second pore generally fused with first pore; nasal canal with two openings in specimen UFBA 3291 (1 CS, 28.6 mm SL; apparently malformation). Infraorbital canal running through entire second infraorbital, extending to infraorbital 1 and generally opening into two pores. Preoperculomandibular branch giving rise to preoperculo-mandibular canal, which runs through entire preopercle with three openings, leading to pores 3, 4, and 5, respectively; pore 3 opening at posterodorsal ridge of hyomandibula in some specimens.

Dorsal fin somewhat triangular, located just posterior to third dorsolateral body plate. Dorsal-fin rays II,8(12), II,9(1), posterior margin of dorsal-fin spine smooth. Nuchal plate generally poorly developed in length and almost entirely exposed, with minute odontodes; anterior tip covered by thick layer of skin ( Fig. 47 ); spinelet extremely short or short; partially exposed; spine poorly developed, adpressed distal tip reaching middle portion of dorsal-fin base; or moderately developed, adpressed distal tip slightly surpassing middle portion of dorsal-fin base; anterior margin with small odontodes. Pectoral fin roughly triangular, its origin just posterior to gill opening. Pectoral-fin rays I,9(13); posterior margin of pectoral spine with 12 to 17 moderately- to well-developed serrations along almost its entire length; small region just posterior to origin of spine lacking serrations; some serrations directed towards origin of spine, perpendicularly directed or directed towards tip of spine; presence of bifid serrations in some specimens; base of branched rays with small laminar expansions on inner margin, generally more evident on first rays ( Fig. 48 ). Anteroventral portion of cleithrum partially exposed; posterolateral portion of scapulocoracoid reduced, externally visible. Pelvic fin oblong, located just below third or fourth ventrolateral body plate, and at vertical through second or third dorsal-fin branched ray. Pelvic-fin rays i,5(13). Adipose fin roughly triangular, separated from posterior origin of dorsal-fin base by six to seven dorsolateral body plates. Anal fin somewhat triangular, located just posterior to 12 th, 13 th or 14 th ventrolateral body plates, and at vertical through origin of adipose-fin spine or region of preadipose platelets. Anal-fin rays ii,5,i(7), ii,6(6). Caudal-fin rays i,12,i(13), generally five dorsal and/or ventral procurrent rays; caudal fin bilobed, dorsal lobe generally slightly larger than ventral lobe.

Two to three laterosensory canals on trunk; first ossicle tubular, second ossicle laminar, third lateral-line canal, if present, encased in third dorsolateral body plate. Body plates with conspicuous line of relatively large odontodes confined to posterior margins; dorsolateral body plates 25(5), 26(7), 27(1); ventrolateral body plates 22(2), 23(10), 24(1); dorsolateral body plates along dorsal-fin base 6(6), 7(7); dorsolateral body plates between adipose-fin spine and caudal-fin base 8(5), 9(6), 10(2); preadipose platelets 3(5), 4(4), 5(4); small platelets covering base of caudal-fin rays; small platelets disposed dorsally and ventrally between junctions of lateral plates on posterior portion of caudal peduncle. Anterior margin of orbit, above region of junction of frontal with lateral ethmoid, with small platelets. Ventral surface of trunk scarcely covered by small irregular or roundish platelets.

Vertebral count 24 (1); ribs 6 (1), first pair conspicuously large; parapophysis of complex vertebra moderately developed ( Fig. 8C ).

Coloration in alcohol. Ground color of body light or brownish yellow, with top of head dark brown. Posterodorsal portion of head, region below eye, opercle and cleithrum with scattered dark brown or black chromatophores; relatively large rounded or irregular black blotches on top of head, becoming gradually smaller towards snout tip. Snout covered by dark brown or black chromatophores on its dorsal surface, generally forming dark brown or black rounded or irregular small spots; with diffuse dark brown or black stripe from anteroventral portion of orbit to upper lip lateral area visible only in single juvenile specimen (MZUSP 88170, 15.4 mm SL); ventrolateral portion of snout variably with dark brown or black chromatophores. Upper lip and maxillary barbel with dark brown or black chromatophores; area of lateral portion of upper lip with conspicuous concentration of dark brown or black chromatophores in some specimens; outer mental barbel with dark brown or black chromatophores, generally more evident on its proximal portion, in some specimens. Dorsal series of four to six dark brown or black blotches, first on anterior portion of dorsal-fin base, second, if present, on middle portion of dorsal-fin base, third on posterior portion of dorsal-fin base, fourth on adipose-fin base, fifth on middle portion of caudal peduncle and sixth, if present, on caudal-fin base; blotches variably diffuse. Dorsal portion of body with conspicuous concentration of dark brown or black chromatophores between counterparts of dorsolateral body plates in some specimens. Ventral surface of body on region posterior to urogenital opening with dark brown or black chromatophores in some specimens. First dorsolateral body plate with conspicuous concentration of dark brown or black chromatophores; posterior margin of some dorso- and ventrolateral plates, and lateral line pores with conspicuous concentration of dark brown or black chromatophores in some specimens. Midline of flank with longitudinal series of four to seven medium-sized conspicuous dark brown or black blotches; blotches rounded, oblong or irregular. Dorsal half of dorsolateral body plates with dark brown or black chromatophores; region of anterior and posterior portions of dorsal-fin base, between dorsal and adipose fins, adipose-fin base, between adipose and base of caudal peduncle and base of caudal peduncle with more concentrated chromatophores, forming conspicuous blotches in some specimens; blotches variably fused to flank midline blotches. Ventral half of dorsolateral body plates and dorsal half of ventrolateral body plates with concentration of dark brown or black chromatophores, forming conspicuous blotches in some specimens; blotches generally more evident on anterior portion of body and on area of flank midline blotches. Mid-ventral portion of ventrolateral body plates on area of flank midline blotches with concentration of dark brown or black chromatophores; forming conspicuous blotches in some specimens; blotches generally more evident posteriorly to pelvic-fin origin; variably fused to flank midline blotches; ventral portion of ventrolateral body plates with concentration of dark brown or black chromatophores, generally more evident posterior to pelvic-fin origin, in some specimens. Dorsal fin with dark brown or black spots; aligned spots, forming somewhat longitudinal or oblique rows in some specimens; small concentrations of dark brown or black chromatophores on some areas of membranes, not forming larger conspicuous dark brown or black patches, in some specimens; larger dark brown or black patch on middle portion of dorsal fin observed only in single juvenile specimen (MZUSP 88170, 15.4 mm SL); dorsal-fin base with conspicuous concentration of dark brown or black chromatophores, generally more concentrated on bases of first, middle and last branched rays; spine covered by dark brown or black chromatophores. Pectoral fin with dark brown or black chromatophores on its dorsal surface, generally more evident on spine and first branched rays; forming dark brown or black spots, generally diffuse and more evident on first branched rays; or entirely hyaline; region of body around dorsal portion of pectoral-fin origin with dark brown or black chromatophores in some specimens. Pelvic fin generally with sparse dark brown or black chromatophores on its dorsal surface; variably forming up to two oblong dark brown or black patches. Adipose-fin membrane with dark brown or black chromatophores; conspicuous concentration of dark brown or black chromatophores in some areas of membrane, generally more evident close to spine, forming isolated patches in some specimens; adipose-fin spine generally with dark brown or black chromatophores. Anal fin with conspicuous concentrations of dark brown or black chromatophores in some areas, generally more evident on its middle portion and bases of last branched rays; variably with one to three dark brown or black blotches; or hyaline. Middle portion of caudal-fin base, posteriorly to last flank midline blotch, generally with small-sized dark brown or black blotch; blotch diffuse or fused with last midlateral blotch in some specimens. Caudal fin with three to six transversal dark brown or black slender bars.

Coloration in life. Similar to that observed in preserved specimens but with ground color of body grayish yellow in some specimens. Body covered by whitish yellow and green iridescent coloration ( Fig. 49 ).

Geographical distribution. Aspidoras maculosus is known from the upper portion of the rio Itapicuru basin, an Atlantic coastal drainage in Bahia State, Brazil ( Fig. 10 ).

Conservation status. Aspidoras maculosus is currently known only from the upper rio Itapicuru basin, Bahia State. Despite the relatively scarce material of this species gathered herein, A. maculosus seems to be more associated with the main channel of rivers, differing from most Aspidoras species, which generally inhabit smaller water bodies. In this way, the smaller number of museum specimens may be related to a practical difficulty in capturing this species in these larger water bodies. Additionally,

no threat to the species as whole is suspected at the present moment. According to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2019), Aspidoras maculosus can be classified as Least Concern (LC).

Material examined. In addition to the material examined by Nijssen, Isbrücker (1976: 119), the following material was analysed. All from Brazil, Bahia, rio Itapicuru basin. MZUSP 88170, 9, 15.4‒30.8 mm SL, rio Paiaiá. UFBA 3291, 2 of 5, 24.7‒26.9 mm SL, 1 CS of 5, 30.7 mm SL, rio Paiaiá. UFBA 4660, 2, 23.4‒24.2 mm SL, rio Itapicuru.

Figures

FIGURE 3 | Dorsal view of the head of CS specimens showing the three patterns of paired frontal bones (outlined in black) in Aspidoras: (A) narrow, with width of each frontal slightly smaller than half of its entire length (Aspidoras maculosus, UFBA 3291, 30.7 mm SL), (B) relatively wide, with width equal to or slightly larger than half of entire length (Aspidoras albater, MZUSP 40793, 29.4 mm SL), and (C) extremely narrow, with width clearly smaller than half of entire length (Aspidoras psammatides, UNT 9604, 27.3 mm SL). Scale bars = 1 mm.

FIGURE 5 | Dorsal view of the infraorbital series of CS specimens showing the four patterns of size and shape of the inner laminar expansion of infraorbital 1 (white arrows) in Aspidoras: (A) extremely well developed (Aspidoras albater, MNRJ 13080, 30.9 mm SL), (B) well developed (Aspidoras fuscoguttatus, NUP 12677, 36.1 mm SL), (C) moderately developed (Aspidoras poecilus, UNT 6249, 30.9 mm SL), and (D) poorly developed (Aspidoras psammatides, UNT 9604, 27.3 mm SL). Abbreviations: io1: infraorbital 1, io2: infraorbital 2. Scale bars = 1 mm.

FIGURE 8 | Ventral view of the complex vertebra in CS specimens of (A) Aspidoras belenos, paratype, UFRJ 4419 (ex-UFRJ 3861), 22.1 mm SL, with well-developed parapophysis, (B) Aspidoras albater, MNRJ 12571, 35.3 mm SL, with poorly-developed parapophysis, and (C) Aspidoras albater, MNRJ 12581 (disarticulated, indeterminate size), with moderately-developed parapophysis. Abbreviations: ccv: centrum of the complex vertebra, pcv: parapophysis of the complex vertebra. Scale bars = 1 mm.

FIGURE 10 | Map showing the geographical distribution of Aspidoras albater (type locality: red circle; non-type localities: black circles), A. aldebaran (type locality: red star; non-type localities: white stars), A. azaghal (purple triangle), A. belenos (type locality: purple diamond), A. brunneus (possible region of type locality: grey diamond), A. carvalhoi (type locality: purple circle), A. depinnai (type locality: red square; nontype localities: black squares), A. fuscoguttatus (type locality: red triangle; non-type localities: white triangles), A. gabrieli (type locality: red pentagon; non-type locality: white pentagon), A. kiriri (black cross), A. lakoi (type locality: red diamond; non-type locality: black diamond), A. maculosus (red cross), and A. mephisto (type locality: white cross). Each symbol may represent more than one locality.

FIGURE 44 | Aspidoras maculosus, holotype, FMNH 54810, 37.2 mm SL, rio Paiaiá, Bahia State, Brazil. Dorsal (top), lateral (middle) and ventral (bottom) views. Photos by Mike Littmann.

FIGURE 45 | Aspidoras maculosus, MZUSP 88170, topotype, 27.8 mm SL. Dorsal (top), lateral (middle) and ventral (bottom) views.

FIGURE 46 | Lateral view of the head of CS specimen of Aspidoras maculosus, UFBA 3291, 30.7 mm SL, showing its general infraorbitals pattern. Abbreviations: io1: infraorbital 1, io2: infraorbital 2, sph: sphenotic, pes: pterotic-extrascapular. Scale bar = 1 mm.

FIGURE 47 | Aspidoras maculosus, UFBA 3291, CS, 30.7 mm SL, showing predorsal region of trunk in dorsal view. Abbreviations: np: nuchal plate, pso: parieto-supraoccipital. Scale bar = 1 mm.

FIGURE 48 | Aspidoras maculosus, UFBA 3291, CS, 30.7 mm SL, showing dorsal view of the pectoral fin. Arrows indicate the small laminar expansions at the base of branched rays. Scale bar = 1 mm.

FIGURE 49 | Uncataloged specimen of Aspidoras maculosus photographed alive. Photo by Angela Zanata.